Solid-state lighting arrays are used for a number of lighting applications. For example, solid-state lighting panels including arrays of solid-state light emitting devices have been used as direct illumination sources, for example, in architectural and/or accent lighting. A solid-state light emitting device may include, for example, a packaged light emitting device including one or more light emitting diodes (LEDs), which may include inorganic LEDs, which may include semiconductor layers forming p-n junctions and/or organic LEDs (OLEDs), which may include organic light emission layers. Typically, a solid-state light emitting device generates light through the recombination of electronic carriers, i.e. electrons and holes, in a light emitting layer or region. A solid-state light emitting device may include, for example, a packaged light emitting device including one or more light emitting diodes (LEDs).
Cree, Inc. produces a variety of products that use LEDs for illumination, such as recessed downlights, troffers and lamps. Solid-state lighting panels are also commonly used as backlights for small liquid crystal display (LCD) screens, such as LCD display screens used in portable electronic devices, and for larger displays, such as LCD television displays.
Solid state lighting devices are typically powered with a constant current signal. However, power is conventionally delivered in AC form. It is therefore generally desirable for a solid state lighting fixture to include an AC/DC converter to convert AC line voltage to a constant current.
Voltage converters can be used to generate DC voltage and/or current from an AC line voltage with high power factor and low total harmonic distortion.
In addition to the high voltage signal needed to power the LEDs, solid state lighting systems also need to generate a low voltage DC signal to power auxiliary circuits, such as a microcontroller, communication systems, ambient light sensors, occupancy (motion detection) sensors, gate drivers, etc. It is typically desirable for many of these auxiliary circuits to remain operational even when the light of the solid state lighting system is turned off. For example, in some cases, it is desirable for the solid state lighting system to be capable of being turned on/off or adjusting the amount of light output in response to a wireless communication signal or in response to an occupancy signal indicating that someone has entered (or left) the room in which the solid state lighting system is installed. Accordingly, instead of completely turning off, the solid state lighting system may instead enter a standby mode in which the light is off but some of the auxiliary circuits remain on.
In general, it is desirable to reduce standby power consumption of solid state lighting systems. The goal of reducing standby power consumption has been recognized by regulatory agencies throughout the world. For example, in Europe, the United States and Canada, energy efficiency standards have been introduced that will require reduction of standby power consumption. Future solid state lighting products may be expected to consume less than 1 W, and in some cases less than 0.5 W of standby power.